Note 6. Net Loss Per Share Attributable to Common Stockholders

The Company calculates basic and diluted net loss per share attributable to common stockholders in conformity with the two-class method required for companies with participating securities. The Company considered all series of convertible preferred stock outstanding prior to the IPO to be participating securities. Under the two-class method, the net loss attributable to common stockholders is not allocated to the convertible preferred stock as the holders of convertible preferred stock do not have a contractual obligation to share in losses.

The diluted net loss per share attributable to common stockholders is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period. For purposes of this calculation, convertible preferred stock, options to purchase common stock and warrants to purchase common stock and convertible preferred stock are considered common stock equivalents but have been excluded from the calculation of diluted net loss per share attributable to common stockholders as their effect is antidilutive. Basic and diluted net loss per share was the same for each period presented, as the inclusion of all potential common shares outstanding would have been antidilutive.

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except per share data):


	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Numerator:
Net loss attributable to common stockholders	$	(5,171	)	$	(8,755	)	$	(18,731	)	$	(23,636	)
Denominator:
Weighted-average common shares outstanding - basic and diluted		40,120			13,884			39,240			13,307
Net loss per common share - basic and diluted	$	(0.13	)	$	(0.63	)	$	(0.48	)	$	(1.78	)

The following weighted-average outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because the impact of including them would have been antidilutive (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Options to purchase common shares		9,224		11,514		10,127		10,862
Restricted stock units		1,829		—		1,257		—
Employee stock purchase plan shares		158		—		207		—
Common stock warrant		11		46		11		36
Convertible preferred shares (as converted)		—		17,645		—		18,040
Preferred stock warrant (as converted)		—		26		—		27
		11,222		29,231		11,602		28,965